Method of machining an oblong workpiece and a machine for performing the method

ABSTRACT

A method of machining an oblong workpiece, which is placed substantially radially in a holding ring and is deformed by cooperation with a roller rotating in the holding ring. In connection with machining of a relatively large amount of material, the workpiece is caused to cooperate with a plurality of differently shaped areas on the surface of the roller. The method is performed by a machine which comprises a rotating holding ring for substantially radial retention of the workpieces. The machine comprises a rotating roller which is placed inside the holding ring and is adapted to machine the radially inwardly directed end of the workpieces. At least two differently shaped types of the machining areas are provided along the surface of the roller, said areas being so disposed that the various types are present radially opposite a workpiece in a predetermined succession at least at the same time as the holding ring performs a corresponding number of entire revolutions.

The invention concerns a method of machining an oblong workpiece, whichis placed substantially radially in a ring-shaped tool and is deformedby cooperation with a roller rotating in a holding ring.

The Danish Patent Specificaiton 143,935 discloses a machine formachinging oblong workpieces and comprising a rotating holding ring forsubstantially radial retention of the workpieces, and comprising arotating roller which is mounted within the tool and is adapted tomachine the radially inwardly directed end of the workpieces. This knownmachine has been a great success for producing nail heads on nailworkpieces. Therefore, it has been attempted to produce as many variantsof nails as possible by means of this known internal rolling principle.However, it has been found that problems arise when a relatively largeamount of material per workpiece is to be machined, i.e. deformed.Examples of such workpieces may be roofing nails or screws.

An object of the invention is to provide a method of the present typewhich makes it possible to machine a larger amount of material perworkpiece than the prior art.

This object is achieved by performing the method in which the roller isdriven relative to the position of the workpieces in the holding ring sothat each workpiece is caused to cooperate with a plurality ofdifferently shaped areas of the surface of the roller. A first treatmentmay comprise moving the workpiece material, and one or more subsequenttreatments may comprise the final shaping. When the method is performedso that the workpieces are subjected to a preliminary deformation in theform of upsetting of material in that the machining areas on the rollercorresponding thereto are provided as mold cavities which extendradially inward toward the center of the roller an upsetting willresult, so that the end of the workpiece to be treated will have amodified diameter to length ratio. When the method is performed so thatthe workpieces are subjected to a preliminary deformation in the form ofshearing, of material transverse to the longitudinal direction of theworkpiece can be obtained.

When the possibilities provided by the method as defined by combiningthe above three methods, there will be so much freedom in shaping theworkpieces that the access angle between the holding ring and the rolleris considerably less critical than is the case in the prior art. Themethod can moreover be performed no matter whether the peripheraI speedsof the holding ring and of the roller are the same. To reduce wear it ispreferred to perform the method.

The method of the invention has special relation to the mentionedmachining by rotating movement. Thus, it is known to forge a head on anail in two working operations to avoid problems because of the limitedflow rate of the material. However, the flow rate is no problem, eitherin the known machine or in the present method where the machining rateof the material is already relatively low because of the rollingmovement.

The various machining areas are preferably distributed on or in thesurface of the roller. When the method is performed so that theworkpieces in the holding ring are distributed with the same mutualdistance and in a number which is not divisible by the number ofmachining areas on the roller, the workpieces can be introduced into theholding ring in a very simple manner. In many uses, there will be justtwo different machining areas on the roller, which entails that theholding must be adapted to receive an odd number of workpieces.

When very accurate machining of material is to be effected over arelatively large radial extent, the shaping areas of the roller may havedifficulty in releasing the workpiece. This problem may be avoided byperforming the method in which following one or more of the machiningprocesses, the workpieces are subjected to final shaping by means ofmachining areas rotatably journalled in the roller and that a machiningarea performs a substantially radial movement with respect to theholding ring from engagement with the workpiece until shaping iscompleted. This method may e.g. be performed by means of tilting toolsjournalled in the roller, but these require relatively much space;however, it will be appreciated that if e.g. two or three differentmachining areas are present on the roller, only the second or the thirdmachining area is to comprise a tilting tool. Therefore, it issufficient to have a limited number of tools so that these do not reducethe strength of the roller.

The invention also concerns a machine of the type which is described inthe above-mentioned Danish patent specification. This machine ischaracterized by the features defined so that at least twodifferentially shaped types of machining areas are provided along thesurface of the roller, the machining areas being so disposed and theroller so driven that the various types of machining areas are presentradially opposite a workpiece in a predetermined succession at least atthe same time as the holding ring performs a corresponding number ofentire revolutions.

In a preferred embodiment, the first type of machining area is arrangedso that a first type of machining area on the group of such areas on theroller are provided as a mold cavity which extends from the periphery ofthe roller radially inward toward the center of the roller with anarrowed cross-section which results in upsetting of the workpiece. Theembodiment of the cavities defined in claim 10 provides a volume ofmaterial as great as possible of the upset material, without thiscausing problems when the cavity releases the workpiece. To obtainlateral shearing of the material, the cavity may be offset. Analternative embodiment for machining areas can bring about shearing ofmaterial transverse to the longitudinal direction of the workpiece.

As mentioned before, the peripheral speeds of the roller and of theholding ring may be the same or different, The gear transmission isadapted i.e. the diameter of the roller, the internal diameter of theholding ring, the number of various machining areas as well as thenumber of groups of machining areas on the roller, and it will beappreciated that the next machining area in a series of treatments of agiven workpiece is not necessarily located in adjacent groups of suchareas. Thus, the mentioned parameters may be varied in many ways. It hasbeen mentioned before that the workpiece material may be moved by meansof the position of the machining area on the roller, but it will also beappreciated that movement of the workpiece material may be providedthrough a difference between the peripheral speeds of the roller and ofthe holding ring.

Of course, it is possible in principle to introduce nail workpieces atany time into the rotating holding ring, but if a workpiece insertionstation is provided radially opposite the holding ring and the stationis adapted to insert workpieces at intervals extending over a pluralityof workpieces in the holding ring corresponding to the number ofmutually different machining areas on the roller, this may be done witha firmly mounted station, while continuously feeding workpiece materialto the station. This avoids discontinuous and reciprocating movementswhen the workpieces are introduced.

An embodiment in which one of the machining areas in each group isprovided as tilting tools having a tilting axis which is disposedoutside the axis of the roller and parallel to it in which the tiltingtools corresponding to each of the machining areas is provided as rollerselections movable in the radial plane of the roller, allows shaping tobe possible over a relatively large radial extent. The machining areacan therefore readily release the workpiece and accordingly provideexact shaping and thus be adapted to calibration. Then, e.g. cross slotsmay be calibrated in screws, where the screw head and at least aninitial machining of the slot may have been performed in one or morepreceding working operations.

The invention will be explained more fully below with reference to thedrawing, in which

FIG. 1 shows a machine of a known type on which the manufacturingprinciple according to the invention is based,

FIG. 2 is a sectional view along the line II--II of the machineillustrated in FIG. 1,

FIG. 3 is a section of a preferred embodiment of a holding ring forcooperation with the roller of the invention,

FIG. 4 shows a preferred embodiment of the machine of the invention,

FIG. 5 is a sectional view of the holding ring shown in FIG. 3 andillustrates a locking mechanism adapted thereto,

FIG. 6 is a side view of a preferred embodiment of a roller of theinvention,

FIG. 7 shows the cooperation of the roller illustrated in FIG. 6 with aholding ring,

FIG. 8 shows a section of the roller and illustrates a preferredembodiment of a machining area provided in this,

FIG. 9 shows another embodiment of the roller of the invention which ishere provided with tilting tools, and,

FIG. 10 shows a section of a third embodiment of the roller, seen fromthe side, and illustrates a cavity for machining a workpiecetransversely to the feeding direction.

Initially, it is illustrated in FIGS. 1 and 2 on which machine and thuson which machining principle the invention is based.

Such a machine is known from the Danish Patent Specification 143 935 andis unique in that the workpieces are machined by so-called internalrolling. FIG. 2 shows a vertical cross-section through the machine shownin FIG. 1, and it will be seen how the holding rings 1 form part of theother constructional members of the machine. It appears that the machineis supported by two opposite plates 2 and 3, the plate 2 beingstationarily secured to a given base, the pIate 3 being pivotallymounted directly opposite the first-mentioned plate. The inner side ofeach of these plates mounts a bearing consisting of an inner ring 4 andan outer ring 5, the outer rings being secured to the inner rings 4 ofthe said bearings, one of said inner rings, viz. the one disposed inconnection with the stationary carrier plates, being internally providedwith a toothing 6, which is adapted to engage with a gear wheel 39mounted on the drive shaft of the motor.

In operation of the machine, the motor drives the two opposed holdingrings via the toothed inner ring in such a manner that the two opposedholding tools placed in said rings indirectly engage each other via theworkpiece and in the vicinity of the machining area, a workpieceradially opposite a machining area being retained in the two opposedholding tools. When a workpiece is present in this position, its head isdeformed corresponding to a mould cavity in the tools facing the ringcentre, and the workpiece is released from the holding tools aftercompleted rolling of the head because of the mutually inclined positionsof the holding rings. This inclination causes an increasing mutualdistance between the holding rings in both peripheral directions awayfrom the position of the machining area radially opposite a workpiecewhere the greatest distance occurs at the common, upper vertex of theholding rings diametrically opposite said machining area. The mutuallyinclined positions of the holding rings are a preferred, known structurewhich involves simplification of the supply of workpieces and release ofthese after machining.

In the prior art, the workpieces are present in the holding rings lessthan an entire revolution, e.g. about 270°, but as will appear from thefollowing, the known arrangement may be changed so that the workpiecesmay be present in the holding rings more than one revolution.

FIG. 3 illustrates a section of a holding ring 9 which is adapted forthe machine and which is known in principle from the Danish PatentApplication 1881/86. The holding ring is thus provided with a groove 10adapted to receive a plurality of holding tools 11 with a plurality ofvarious spacer tools 12 and 13 between each of these, said spacer toolsbeing distributed according to a determined pattern and being moreoverclamped in a direction toward the bottom of the groove, i.e. in theaxial direction of the holding ring. Thus, the spacer tools 12 and 13firmly position the holding tools 11 in the circumference of the holdingring by means of wedge effect, since both the holding and the spacertools are provided with side faces which cut a plane, defined by theholding ring, in lines which are parallel with a groove 14 formed in theface of the tool. It will thus be appreciated that the radial pressureforces occurring in this structure between the roller 8 and the rollpath formed by the holding tools 11 cannot be transferred to the otherholding tools, disposed in the groove, in the entire circumference ofthe holding ring 9.

This constructional principle for the holding ring is important inconnection with the new structure of the machine of the invention,because it is intended precisely for machining of workpieces where greatmovements of material may be necessary. As mentioned before, the machineis to handle workpieces which are to undergo two or more machiningprocesses, and this is particularly important when the mentioned greatmovements of material are to be provided, such as e.g. for nails, screwsor the like with large heads. To enable such deformations, the shapingaccording to the invention is divided into two or more sub-processes.

To produce workpieces in several process steps, the roller of theinvention is therefore provided with mould cavities adapted to theindividual types of workpieces, like the mentioned holding tools. Thesemould cavities move the workpiece material downwardly and sideways withrespect to the mould cavities of the holding tools prior to the finalrolling. This embodiment of the roller face will be described more fullybelow.

FIG. 4 is an overall illustration of an embodiment of the machine of theinvention, and shows the novel components. It will thus be appreciatedthat this novel structure involves considerably increased flexibility inthe fields of use of the machine since it is now possible to satisfymany different shape requirements thanks to various roller types and/orholding tools.

It should be mentioned that the known machines of this type arepreferably driven so that the holding rings and the associated rollerrotate with different peripheral speeds, the speed of the roller beingpreferably greater than that of the holding ring. The reason for theselection of such coaction between the roller and the holding ring isusually that, after contact with the roller, the workpiece is to besubjected to action in the feeding direction to obtain a better initialshaping.

However, this principle is not required in the machine of the invention.Owing to the fact that two or more initial part treatments of theworkpieces can be obtained with the machine of the invention, thisperipheral speed difference is no longer a practical necessity, so thatwear on the engagement faces is reduced considerably. It has also beenfound to be easier to control the deformation sequence, in particularwhen moving relatively large masses of material, which has been solvedaccording to the invention by a special arrangement of the roller.

Thus, FIG. 4 shows a preferred embodiment of the machine where theroller is provided with two different types of machining areas which arealternately disposed with the same mutual distance, one machining area16 being adapted to pre-shape the inwardly extending free portion of theworkpiece, while the immediately following machining area is to performthe final rolling, after which the workpiece is finished.

The first machining area 16 is, as appears from the figure, provided asa radially inwardly extending cavity 16, which is substantially in theform of a truncated cone whose axis coincides with a radius of theroller. The cavity 16 has this shape because of the deformation sequencewhich the free portion 17 of the workpiece 18 has, where this portion 17is upset to the said truncated cone shape by the deformation. It will beappreciated that this shape is advantageous because so much material aspossible is moved radially outwardly in the holding ring after the firstshaping process. When the axial cross-section of the upset workpiecehead 20 is narrowed upwardly, it will be appreciated that thedeformation path and thus the flowability requirements are reduced, andat the same time a better filling of the mould cavity 21 of the holdingtool is obtained.

FIG. 4 shows a starting workpiece 18 which is disposed in a positionjust before its free portion 17 is to undergo a first deformationprocess by coaction with the oppositely disposed cavity 16. The sameworkpiece is shown at 20 after upsetting. Since, as mentioned, thisworkpiece is to be subjected to a further process, it is to be movedwith the holding ring another revolution while being still retained, sothat the head 20 of the workpiece then undergoes the final machining viathe roller face 15, whereby the head of the workpiece has been given itsfinal shape and is finished. Then the workpiece is moved on for releasefrom the holding rings. For this operation to be feasible, it isnecessary to have a switching mechanism which is so adapted thatworkpieces that have still not been finished are allowed to pass therelease location and be moved with the holding rings while being stillretained up to the mentioned final rolling process. This switchingmechanism may be provided as a so-called timer wheel 22 and a guide rail23 cooperating with it.

The timer wheel 22 is peripherally provided with notches 24 with amutual arc distance, which corresponds to the arc length between everysecond workpiece, externally on the holding ring, said timer wheel beingrotated with a peripheral speed corresponding to that of the holdingring.

The timer wheel 22 is so geared with respect to the positions of theworkpieces in the holding ring that the locking pawls 25, which extendradially outwardly from the outer side of the holding ring to retainfinished workpieces, will contact a release face 26 on the timer wheel.The release pawl Z5 is hereby forced outwardly and releases a lockingdevice in the holding ring, following which the workpiece is finallyreleased by a projecting means 46. Upon further rotation of the holdingring, the pawl 25 is moved in its releasing position to the said,adjoining guide rail 23, which for this purpose is provided with twoguide faces 27 and 28 displaced in the radial direction of the holdingring. Thus, the locking pawl 25 leads into the radial innermost guideface 27 of the guide rail 23 whereby the locking mechanism is held in areleased position forwardly to a feed device or guide pin 29, where anew workpiece is fed to the empty holding tool.

In contrast to the foregoing workpieces which have just undergone thefirst shaping process will be moved toward the timer wheel 22 in such amanner that the locking pawls 25 associated with these workpieces willbe received in the notches 24 of the timer wheel, so that the workpiecesare still retained, and so that a guide pin 29 mounted for the purposein a radial extreme position on the locking pawl engages the said secondguide face 28 of the guide rail, which causes the workpiece to still belocked in the further feeding to the final machining.

The said locking mechanism 27, which is of known type, is illustrated inFIG. 5 and operates in that the locking pawl 25, which is rotatablysecured to a pin 38 and is biased via a spring 39, can be forcedradially into the holding ring, so that a locking eccentric 40, providedin a slidably journalled bushing, can be rotated to a non-lockingposition where the locking pawl 25, likewise after insertion of aworkpiece, moves into its locking position.

New workpieces are inserted into the empty holding tools by means of afeed device adapted for this (a so-called manipulator) 29, which, toensure correct insertion time, is so geared with respect to the rotationof the holding ring that insertion of a workpiece takes place preciselywith intervals corresponding to the time for the passage of twice thearc length between two workpieces.

It will be appreciated that workpieces are to be inserted at arelatively great speed, which takes place by continuous rotation of theholding ring. To arrest the workpiece at the insertion, a positioningroller 30 is provided, said roller being adjustable in connection withvarious workpiece shapes. This roller positions the workpiece radially alittle too far inwardly to ensure sufficient material, and upon furtherrotation the workpiece meets another, fixed positioning roller 31 whichis adapted for the final, radial positioning of the workpiece beforethis is subjected to the first deformation.

In the shown preferred embodiment, the roller 8 is provided with twodifferent machining areas, so that the total number of machining areasin the circumference of the roller is an even number. This is becausethe number of workpieces in the holding ring may not be divisible bymultiple of the number of various types of machining areas on the rollerso as to ensure that the individual workpiece in the holding ring willbe subjected to the correct shaping process when returning to themachining area radially opposite to this, which is tantamount to theroller and the holding ring, after each revolution of the latter, havingbeen displaced precisely an arc section corresponding to a multiple ofthe distance between two machining areas.

It will likewise be appreciated that the roller may be provided withanother number of various machining areas, in accordance with adaptingthe above-mentioned proportion between machining areas and the number ofworkpieces in the holding ring.

In FIG. 6, the roller 8 is illustrated as seen from the roller side, sothat the mentioned mould cavities 16 and the roller areas 41 disposedbetween these are visible.

FIG. 7 shows an enlarged section of the roller 8, which corresponds inprinciple to the view of FIG. 4, but the roller is here provided with amould cavity 32 which differs from the above-mentioned cavity in that,when disposed radially opposite a workpiece, it is displaced a distancein the feeding direction, which entails that the mass of material upsetby this is correspondingly moved ahead with respect to a plane throughthe axis of the workpiece and the centre of the roller.

This structure of the roller counteracts the flowing of materialotherwise occurring which causes the material to tend to be pushed inthe direction opposite the feeding direction, so that, after completedprocess, the distribution of the material will be disuniform. It is thuspossible to produce heads for oblong objects having a considerablyimproved size and finish.

FIG. 8 shows another embodiment of the mould cavities of the roller. Aswill be seen, the truncated cone shape 16 and 32 has been replaced by asubstantially paraboloid cavity 33. This shape is particularlyadvantageous since the natural flow of the material follows a paraboloidshape, so that some of the frictional forces, which would otherwiseoccur by upsetting according to the above-mentioned cavities, will beremoved, which is important in connection with the already great flow ofmaterial in the process, and which, of course, reduces the risk ofcracks and ruptures in the machined material. It also appears, asindicated at 42 in the figure, that the requirement in respect of thenecessary cavity depth has been reduced. To avoid pressure or tearingimpacts on the truncated cone material 20 when the cavity leaves thetruncated cone, the cavity may be rounded, as indicated at 34, so as toensure a correctly shaped and unaffected workpiece cavity 20, whilereducing wear on the roller.

FIG. 9 illustrates the principle of an alternative embodiment of theroller. The machining areas of the roller are movable so that thecontact face of the machining area from engagement with a workpiece isconstantly disposed radially opposite said workpiece until the contactface of the machining face releases the workpiece machined.

This manufacturing method is possible in that the movable machiningareas or so-called tilting tools 43 are arranged as circular discs whichare journalled around their axis, somewhat radially inwardly toward theroller centre at a distance which is slightly smaller than the radius ofthe tilting tool. Thus, part of the circular tilting tool protrudesradially from the roller periphery, said part, viz. the machining face38, having been planed for engagement with an oppositely disposedworkpiece. It will be appreciated that the face 38 may be provided withdifferent forms of stamping contours, such as a cutting tool for cuttingslots on screws.

It will likewise be appreciated that the tilting tools may be sojournalled in the roller that there is spring mechanism (not shown) forbiasing the tilting tools so that these, after having released theworkpiece in question, rotate back to their starting position shown at37.

With the above-mentioned structure, there is thus provided a rollerwhich entails that the machining area on the tilting tools are capableof performing longitudinal and transverse, translatory movementssimultaneously, which, as mentioned, is of importance in the productionof relatively deep stamping contours. It will be appreciated that inaddition to the tilting tools the roller may have other machining areas,which is symbolized in the figure by the presence of two workpiecesbetween the workpieces cooperating with the tilting tools.

FIG. 10 shows another embodiment of the roller of the invention wherethe machining areas comprise mould cavities 45 which, in contrast to theabove-mentioned cavities, serve to provide bending of the free portionof the workpiece in directions transverse to the feeding direction,following which the workpiece is subjected to final rolling. Suchinitial shaping is adapted to be used in connection with the productionof objects having D-shaped heads, where the straight edge of the head isparallel with the feeding direction in the holding ring. Thisorientation is known from the Danish Patent Application 3490/79 andprevents formation of burrs.

I claim:
 1. A method of machining an oblong workpiece (18), which isplaced substantially radially in a ring-shaped tool and is deformed bycooperation with a roller (8) rotating in a hold ring (1), comprisingdriving the roller relative to the position of the workpieces in theholding ring so that each workpiece is caused to cooperate with aplurality of differently shaped areas (16) of the surface of the roller.2. A method according to claim 1, wherein the workpieces are subjectedto a preliminary deformation in the form of upsetting of material inthat the machining areas on the roller corresponding thereto areprovided as mould cavities (22) which extend radially inwardly towardthe centre of the roller.
 3. A method according to claim 1, wherein theworkpieces are subjected to a preliminary deformation in the form ofshearing of material transverse a the longitudinal direction of theworkpiece.
 4. A method according to claim 1, wherein the rollercomprises a plurality of machining groups, each of which has a pluralityof mutually different machining areas, and that the roller is drivenrelative to the position of the workpieces in the holding ring so that aworkpiece is caused to cooperate with a predetermined succession of thevarious machining areas (16 and 41).
 5. A method according to claim 1,wherein the roller and the holding ring cooperating with it are drivenwith the same peripheral speed.
 6. A method according to claim 1,wherein the workpieces in the holding ring are distributed with the samemutual distance and in a number which is not divisible by the number ofmachining areas on the roller.
 7. A method according to claim 1, whereinfollowing one or more preceding machining processes the workpieces aresubjected to final shaping by means of machining areas (44) rotatablyjournalled in the roller, and that a machining area performs asubstantially radial movement with respect to the holding ring, fromengagement with the workpieces and until completed shaping.
 8. A machinefor machining oblong workpieces (18) and comprising a rotating holdingring (1) for substantially radial retention of the workpieces andcomprising a rotating roller (8) provided within the holding ring tomachine the radially inwardly directed end (17) of the workpieces,wherein at least two differently shaped types of machining areas (16 and41) are provided along the surface of the roller, said machining areasbeing so disposed and the roller so driven that the various types ofmachining areas are present radially opposite a workpiece in apredetermined succession at least at the same time as the holding ringperforms a corresponding number of entire revolutions.
 9. A machineaccording to claim 8, wherein a first type of machining areas on thegroups of such areas on the roller are provided as a mould cavity (32)which extends from the periphery of the roller radially inwardly towardthe centre of the roller, with a narrowed cross-section.
 10. A machineaccording to claim 9, wherein said mould cavity is partly defined by aparaboloid-of-revolution wall.
 11. A machine according to claim 9,wherein the equidistantly spaced mould cavities (32) corresponding tothe machining areas on the roller are displaced a distance forwardlywith respect to the other machining areas of the roller so that an axisof the mould cavity through the centre of the roller is disposed in aplane displaced from the axis of the workpiece when the cavity ispresent radially opposite such a workpiece.
 12. A machine according toclaim 8, wherein a second type of machining areas (45) in the groups ofsuch areas in the roller is provided as shaping projections havingshaping faces which form an angle with a common radial plane for theholding ring and the roller.
 13. A machine according to claim 8, whereinthe roller and the holding ring are driven by means of a gear mechanism(6 and 39), which has such a transmission that the roller is driven witha peripheral speed so adapted with respect to the positions of theworkpieces in the holding ring that the workpiece is caused to cooperatewith a predetermined succession of mutually different machining areas inthe groups of such areas of the roller.
 14. A machine according to claim8, wherein a workpiece insertion station (29) is provided radiallyopposite the holding ring and that the station is adapted to insertworkpieces at intervals extending over a plurality of workpieces in theholding ring corresponding to the number of mutually different machiningareas on the roller.
 15. A machine according to claim 14, wherein theroller is divided into a plurality of groups, each of which comprises atleast two different machining areas along the surface of the roller, andthat the holding ring is adapted to receive an odd number of workpieces.16. A machine according to claim 8, wherein one of the machining areas(44) in each group is provided as tilting tools (43) having a tiltingaxis which is disposed outside the axis of the roller and parallel withit, the tilting tools corresponding to each of said machining areasbeing provided as roller sections movable in the radial plane of theroller.
 17. A machine according to claim 16, wherein the machining areaadapted for the final shaping consists of a tilting tool (43) which isadapted to perform a final, calibrating function.